Integrated circuit fabrication frequently comprises forming openings over regions, and subsequently filling the openings with various materials.
One type of integrated circuitry is complementary metal oxide semiconductor (CMOS) sensor circuitry, which may be utilized for detecting electromagnetic radiation. For instance, CMOS sensor circuitry may be utilized in digital cameras for detecting light.
Several layers may be built over the CMOS sensor circuitry to improve sensitivity of the circuitry and/or to alter sensitivity of the circuitry for different wavelengths of light. For instance, a Bayer filter may be formed over the CMOS sensor circuitry as a combination of red, green and blue filters to create regions of the CMOS sensor circuitry that are sensitive to particular wavelengths of radiation. As another example, microlenses may be formed over regions of the CMOS sensor circuitry to enhance light-gathering by the CMOS sensor circuitry.
The Bayer filter may be formed of material deposited over a semiconductor substrate, and similarly the microlenses may be formed of material deposited over a semiconductor substrate. For instance, the Bayer filter may comprise dyed photoresist, acrylic material, etc.; and the microlenses may comprise polyimide, thermoplastic, thermoset resin, photosensitive gelatin, radiation-curable resin, etc.
It may be desired to form one or both of the microlenses and the filters within openings over the CMOS sensors. Difficulties may be encountered in attempting to align the openings with the CMOS sensors. Accordingly, it is desired to develop new methods of forming openings.
Openings are utilized in many other applications besides fabrication of lenses and filters for CMOS sensors. Difficulties may be encountered in attempting to align openings in such other applications, and accordingly it is desired to develop methods which may be generally applicable for alignment of openings during semiconductor fabrication.